Chapter 2: Properties of Chapter 2: Properties of MatterMatterChemistry

2.1 Classifying matter:2.1 Classifying matter:Composition: the combining of parts

into a whole

Pure substances: always have exactly the same composition

◦Examples: table salt, sugar

◦Uniform composition= samples have the

same properties

◦Can be classified into: elements and

compounds

ElementsElementsSubstance that can’t be broken into

simpler substances

◦~100 exist

Atom: smallest particle of an element

Fixed composition: contains one type

of atom

Each element has a specific type of

atom

ElementsElementsExamples:

◦Solids- aluminum, carbon◦Gases- oxygen, nitrogen◦Liquids- only 2 are liquid at room

temperature [mercury and bromine]

Symbols: ◦1813, Berzelius (Swedish chemist)◦One or two letters

1st capitalized and 2nd lower case◦Based on Latin names of elements

i.e.: gold = Au or aurum◦Easy communication

CompoundsCompoundsContains 2 or more elements

joined in a fixed proportion

◦2 hydrogen to 1 oxygen = water ◦Properties are different from the

individual substances that they are made of

◦ie: oxygen and hydrogen versus water

MixturesMixtures2 or more substances that are not

chemically combined and can be separated

◦Properties can vary: composition is

NOT fixed◦Can retain properties of the

substances being combined◦Classified by how well distributed the

substances are in the mixture

Heterogeneous & Homogeneous Heterogeneous & Homogeneous MixturesMixturesHeterogeneous: parts of a mixture

are noticeably different from one another◦ie: sand, salad◦“hetero” = different; “genus” = kind

Homogeneous: substances are distributed evenly & it’s hard to tell one from another◦Appears to be made of one substance◦ie: water in a swimming pool, stainless

steel

Solutions, Suspensions, and Solutions, Suspensions, and ColloidsColloids

Def: based on size of the largest

particlesSolution: when substances dissolve

and form a homogeneous mixture

◦ie: tap water, windshield wiper fluid

◦1. Do not separate into layers over time

◦2. Cannot filter to separate

◦3. Allows light to pass through

SuspensionsSuspensionsDef: a heterogeneous mixture that

separates into layers over time

◦“Shake well before using”

◦ie: sand in water

◦1. Can be filtered to separate

◦2. Appear “cloudy”

◦3. Scatter light in all directions

ColloidsColloids

1. Do not separate into layers

2. Cannot use a filter to separate

3. Scatters light

ie: fog, homogenized milk

2.2 Physical Properties2.2 Physical PropertiesDef: any characteristic observed

or measured without changing the composition of the substance(s)

Examples: viscosity, conductivity, malleability, hardness, melting point, boiling point, and density

ViscosityViscosity

Def: a liquid’s resistance to flowing

◦Greater viscosity = slower the liquid flows

◦Lower viscosity = faster the liquid flows

◦Honey is more viscous than water

◦Usually decreases when heated (thins

out)

◦ie: Motor oil has to have the correct viscosity in different temperatures

ConductivityConductivity

Def: a material’s ability to allow heat to

flow

◦Conductors: have high conductivity

Metals

Usually a good conductor of electricity

◦Insulators: have low conductivity

Woods

Usually a bad conductor of electricity

MalleabilityMalleabilityDef: ability of a solid to be

hammered without shattering

◦Most metals (gold) are very malleable

◦Ice and glass are not very malleable

◦Brittle: solids that shatter when struck

HardnessHardness

Def: how hard a solid is

◦Compare by scratching one material on

another

◦Kitchen knife against copper sheet

◦Diamond is the hardest known material

Melting, Boiling, and Melting, Boiling, and DensityDensity

Melting and boiling points:◦Melting point- temp at which substance

changes from solid to liquid◦Boiling point- the temp at which

substance changes from liquid to vapor

◦Specific to each compound or elementDensity: ratio of mass to volume

(g/cm3)◦Used to test purity of a substance

Separating MixturesSeparating MixturesFiltration: separates materials

based on size of particles

◦ie: coffee filters, wire screen

Distillation: separates substances in a solution by boiling point

◦i.e.: fresh water for submarines

2.3 Chemical 2.3 Chemical PropertiesProperties

Def: ability to produce a change in the composition of matter◦observed when substances change

into different substances

Examples: flammability and

reactivity

Flammability and Flammability and ReactivityReactivity

Flammability: material’s ability to burn in the presence of oxygen◦ie: gasolines, fabrics, drywall

Reactivity: how readily a substance combines chemically with other substances◦oxygen with iron and water = rust◦nitrogen gas can be used to slow rust

production

Chemical & Physical Chemical & Physical ChangesChangesPhysical Change: properties change, but substances stay the same◦ ie: phase changes, slicing foods, crumpling

paper◦Most can be reversed, but not all

Chemical change: substance reacts and forms one or more new substances ◦ ie: baking/cooking, food digesting◦1. Unexpected change in color◦2. Production of a gas◦3. Formation of a precipitate

Chemical versus Physical Chemical versus Physical ChangeChange

Are different substances present

after?

◦Yes- chemical change

◦No- physical change

Examples?

Chapter 3: States of Chapter 3: States of MatterMatter

3.1 Solids, Liquids, and 3.1 Solids, Liquids, and GasesGasesStates of Matter: classified based on whether

shapes and volumes are definite or variable

◦Solids: definite shape & definite volume

ie: pencil, desk, chalkboard

Orderly arrangement of particles at atomic level

◦Liquids: take shape of container & definite

volume

ie: water at room temp, pop, juice

Slightly random arrangement of particles at atomic

level

Gases and Other StatesGases and Other StatesGases: no definite shape and no definite

volume◦ ie: helium, “air,” natural gas◦Takes the shape and volume of its container ◦Random arrangement of particles at the

atomic level◦volume: can be compressed or expanded

Plasma: ◦99% of all observable matter◦Extremely high temperaturesBose-Einstein BEC: predicted by Einstein in the 1920s, accepted

in1995 -273oC, extremely low temperatures Groups of atoms behave as a single particle

Kinetic Theory:Kinetic Theory: Gases GasesDef: all particles of matter are in constant

motion◦Kinetic energy: energy an object has due to

motion

Gases: constant motion allows gases to fill containers of any size/shape

◦Constant, random motion

◦Motion of particles unaffected by other particles (unless in collision)

◦Forces of attraction among particles can be ignored most of the time

Kinetic Theory: Liquids & Kinetic Theory: Liquids & SolidsSolids

Liquids: particles have motion slower than gases & faster than solids◦ Particles flow to new locations & take shape of

container

◦ Volume constant because forces of attraction keep particles close together

◦ ie: students moving through crowded hallways, airports

Solids: particles have “slowest” motion, vibration◦ Definite shape and volume

◦ Particles vibrate around fixed locations

◦ ie: people in a movie theater, in a car on a road trip

3.3 Phase Changes3.3 Phase ChangesPhase change: reversible, occurs when

a substance changes from one state to another◦Common phase changes: melting,

freezing, vaporization, condensation, sublimation, and deposition

Temperature: the temp of a substance does not change during a phase change◦Phase change graphs◦Melting point = freezing point◦Boiling point = condensation point

Energy and Phase Energy and Phase ChangesChanges

Energy is absorbed or released during

a phase change

◦Endothermic: system absorbs energy

ie: ice melting

◦Exothermic: system releases energy

i.e.: water freezing into ice

Melting and FreezingMelting and FreezingMelting: endothermic; going from solid to liquid

Molecules gain energy to overcome attractions between particles

◦ Complete: all particles have enough energy to “flow”

Freezing: exothermic; going from liquid to solidMolecules release energy and attractions between

particles have effect

◦Complete: particles vibrate in place

◦Solids at room temperature freeze at very high temps

VaporizationVaporizationDef: substance changes from liquid to gas, endothermic

Evaporation: liquid gas at temps below the boiling

point

◦ Takes place at the surface of a liquid

◦ Vapor- gas phase of a substance that is usually solid or

liquid at room temp

◦ Vapor pressure- caused by collisions of vapor and walls

of a container

Boiling: vapor pressure becomes = to atmospheric

pressure

◦ Molecules below surface have kinetic energy to overcome

particle attractions

◦ Bubbles quickly rise to the surface & burst

CondensationCondensationDef: substance changes from gas or

vapor to liquid

◦Exothermic

◦i.e.: Fog on mirror, dew on grass

Sublimation and Sublimation and DepositionDepositionSublimation: substance changes

from solid to gas or vapor without changing to a liquid 1st ◦Endothermic ◦ie: dry ice

Deposition: gas or vapor changes directly into solid without 1st changing to a liquid◦Exothermic◦ie: frost on windows